This invention relates to lifting frames and to methods of lifting prefabricated building modules.
There are various applications wherein it is desired to lift relatively large, heavy and bulky elongated loads having asymmetrical or lopsided weight distributions in the direction of elongation. Typical of these is the erection of various kinds of prefabricated buildings wherein the building is formed, in whole or in part, by elongated room-size prefabricated building modules. In such case, the building modules are fabricated at a factory site, loaded aboard trucks, railroad cars or other means of transportation, transported to the building erection site and then set into place to form the desired building structure. At various points in this process, it is desired to lift the prefabricated building module. At the factory site, for example, it is desired to lift the building module onto the truck or other form of transportation. At the building erection site, it is desired to lift the building module off of the truck or other form of transportation and to set it in place relative to the remainder of the building structure.
A preferred method of lifting prefabricated building modules of the foregoing type is to use a lifting crane or hoisting mechanism which is coupled by means of cables or the like to appropriate cable attachment devices which are located on or form part of the building module. This method is described in varying degrees in the following issued patents:
1. U.S. Pat. No. 1,362,069 granted to J. R. Witzel on Dec. 14, 1920 for a "Building Construction"; PA1 2. U.S. Pat. No. 3,103,709 granted to H. C. Bolt on Sept. 17, 1963 for "Building Structures"; PA1 3. U.S. Pat. No. 3,162,863 granted to A. L. Wokas on Dec. 29, 1964 for "Prefabricated Bathrooms And Prefabricated Restrooms"; and PA1 4. U.S. Pat. No. 3,461,633 granted to R. L. Ziegelman et al. on Aug. 19, 1969 for a "Prefabricated Building Structure". PA1 1. U.S. Pat. 3,015,407 granted to N. W. Fesmire et al. on Jan. 2, 1962 for "Stacking Cargo Containers"; PA1 2. U.S. Pat. No. 3,078,115 granted to L. A. Harlander et al. on Feb. 19, 1963 for a "Lifting Beam "; PA1 3. U.S. Pat. No. 3,501,193 granted to R. L. Gray on Mar. 17, 1970 for a "System For Engaging Cargo Containers"; PA1 4. U.S. Pat. No. 3,596,970 granted to R. Levert et al. on Aug. 3, 1971 for "Mechanical Gripper Frame Unit Lifting Devices For Parallel-Walled Containers Or The Like"; and PA1 5. British Patent No. 1,160,860 published on Aug. 6, 1969 and describing "Improvements In Or Relating To Adjustable Frames For Lifting Containers".
A problem not mentioned by the above-listed patents relates to the fact that there will be various situations in which the weight of the building module or the combined weight of the building module plus equipment pre-installed therein is distributed in an asymmetrical or lopsided manner with respect to the direction of elongation of the building module. In other words, the center of gravity of the building module from a weight standpoint may be located a substantial distance to one side of the physical or geometrical centerpoint of the building module. This may occur because the total weight of the building materials nearer one end of the building module is greater than the total weight of the materials nearer the other end. For example, there may be more windows or doors or interior wall partitions nearer one end than the other.
Also, for purposes of expediting the completion of the building to be erected, it is sometimes desirable to pre-install into the building module at the factory site as much of the equipment to be used in the final building structure as is possible. For example, it may be desirable to install at the factory site the various plumbing and toilet fixtures, the heating and air conditioning equipment and various other built-in type fixtures and equipment. For industrial and commercial type buildings, it may even be desirable to install items such as industrial equipment and machinery, business equipment and fixtures and the like in the building modules before they are transported to the building erection site. In general, such pre-installed items will not be evenly distributed from a weight standpoint. For this reason also, the building modules to be transported to and set in place at the building erection site will not, in many cases, have a symmetrical weight distribution.
The building modules being considered may weigh upward of 10 tons or more. They are relatively large, heavy and bulky. A typical module may have, for example, a length of 40 feet, a width of 12 feet and a height of 10 feet. As a consequence, if the centerline of lift of the lifting crane or hoisting mechanism is not located directly above the center of gravity of the building module, there will be a considerable tendency for the building module to tip or tilt when being lifted by means of a cable-type lifting sling. Provision can, of course, be made for preventing slippage of the lifting sling cables relative to the hook of the lifting crane. This, however, would cause the lifting sling cables attached to the heavier end of the building module to carry a greater proportion of the load and might cause breakage of same. Also, where the weight distribution is very lopsided, this would not always prevent some tipping or tilting.
The above-listed patents do not explore this question of lopsided weight distribution. The lifting systems and devices described in these patents are such as would be used where the center of gravity of the building module coincides with the physical centerpoint of the building module.
Another and different field of human endeavor where the lifting of relatively heavy loads is encountered is the freight shipping business wherein freight is shipped in relatively large, box-like cargo shipping containers. One technique sometimes used in handling and lifting such cargo shipping containers makes use of a detachable lifting frame which is releasably fastened to the upper portion of the shipping container. A lifting crane or hoisting mechanism is the coupled to the lifting frame for purposes of lifting and moving the shipping container. This technique for handling cargo shipping containers is described in various ways and to varying degrees in the following issued patents:
With the exception of the British Patent, none of these cargo shipping container patents makes any mention of the problem involved in handling loads having asymetrical or lopsided weight distribution. In keeping with this fact, none of the lifting frames described in the first four of these patents includes any features which might be used to compensate for lopsided weight distributions.
The above-listed British Patent describes an adjustable lifting frame for lifting cargo shipping containers having lopsided weight distributions. The lifting frame described in this patent includes a main beam structure which can be releasably fastened to the top of a shipping container. An auxiliary beam is located above and attached to the main beam structure. The auxiliary beam is, in turn, supported by a suspension member in the form of a cradle structure having rollers which engage and support the underside of the auxiliary beam. Such suspension member also includes a crane hook eye located above the auxiliary beam for engagement with the hook of a lifting crane. An electric drive mechanism is provided for causing the cradle-like suspension member to move longitudinally along the auxiliary beam.
The lifting structure described in this British Patent is relatively expensive and complicated. It is not adapted for use with a cable-type lifting sling and, as such, lacks the flexibility and stability of the latter. Also, it does not appear to be very well suited for use in lifting relatively long and relatively heavy building modules.
In accordance with the invention, there is provided a new and improved lifting frame for enabling an elongated room-size prefabricated building module or other large, heavy and bulky elongated load having an asymmetrical or lopsided weight distribution to be lifted with a minimum of tipping, tilting or undesired shifting or such module or load during the lifting process.
The issued patents discussed above were found during the course of a prior art investigation of reasonable scope and effort. They represent what applicants presently consider to be the best of the prior art presently known to them. No representation is made or intended, however, that better prior art does not exist. Nor is any representation made or intended that the foregoing interpretations are the only interpretations that can be placed on these patents.